UV disinfecting units are widely used in building heating, ventilation, and air cooling (HVAC) systems to kill and remove germs, fungi, and other pathogens carried in the air in order to improved the healthiness of indoor environments. A UV disinfecting unit is typically inserted at a suitable place in the return air ducting in order to kill the pathogens before they are carried into the HVAC unit and re-delivered into the inlet ducting into the building spaces. The UV unit contains one or more UV lamps which radiate ultraviolet light to kill pathogens carried in the air processed through the unit. Since the UV lamps can be harmful to human beings as well, they must be completely enclosed during operation of the UV unit, and shut off when the UV unit is opened, such as during maintenance. In U.S. Pat. No. 5,894,130, for example, a UV sterilization unit is positioned in the air return duct and has UV lamps carried in a cartridge which is interlocked with a disable switch for safety during maintenance.
UV units in HVAC systems have not been highly efficient in microbe killing capacity due to the high volumes of air required to be processed through HVAC systems resulting in a relatively low amount of UV exposure of pathogens per unit volume of air processed. In addition, HVAC systems often have multiple return air ducts leading to a single HVAC unit, so that if a UV unit in one return duct is operating at low efficiency or malfunctioning, the pathogens passed through the one unit will be spread to all building spaces when the air is carried into the HVAC unit and re-delivered to the inlet ducting into the building spaces. Furthermore, many buildings and individual offices spaces are not serviced by an HVAC system, but may have individual air conditioners installed in individual offices with no UV disinfecting capability.
With the recognition that indoor air is a major source of allergens and pathogens harmful to people in indoor spaces, some manufacturers have offered individual UV units which can be installed in a ceiling of a room or office space, or in the input duct delivering conditioned air to an individual space. Some units have combined air filtering with UV disinfecting in order to perform the combined functions of removing particulates and allergens from the air as well as killing microbes and pathogens. The conventional units typically have an inlet for an incoming air stream, a filter for removing particulates from the incoming air stream, a cavity space to channel the air stream past one or more UV lamps for killing pathogens, and a blower for moving the air through the unit to an outlet. The conventional units have common problems such as low air throughput, high blower noise if a large blower is used to increase throughput, low microbe kill rate due to inefficient UV exposure, and low air moving efficiency in terms of cleaning the majority of air contained in a room through at least several air changes per hour.
The present invention seeks to provide an improved system having high-throughput, high-volume, and highly effective air cleaning and disinfecting of pathogens in room air spaces.